CHAPTER FOUR
4-8
bc620/627AT Time and Frequency Processor
Symmetricom, Inc.
The packet format is as follows:
byte 1
SOH.
byte 2
“G.”
byte 3
ASCII “±” (advance/retard).
byte 4
ASCII “0” - ”9” (most significant digit).
. .
. .
byte 10
ASCII “0” - ”9” (least significant digit).
byte 11
ETB.
* * * WARNING * * *
If offsets larger than +/- 990 microseconds are used, then the TFP jamsynch feature must be
turned off using packet “P.” The reason for this requirement is that under normal operation if a
difference between the reference time and the TFP time is detected to be greater than +/- 1
millisecond the TFP time base is “jammed” to the reference time so that a lengthy steering
process is avoided.
4.1.7 PACKET “H” - SET TIME CODE FORMAT FOR MODE 0
Packet “H” allows the host to select the format and modulation type. The packet format is as
follows. The time code format and modulation values are maintained in battery backed RAM.
byte
1
SOH.
byte
2
“H.”
byte
3
Format.
byte
4
Modulation.
byte
5
ETB.
Format Choices
“A”
IRIG A.
“B”
IRIG B.
“C”
2137 (XR3 with 100 Hz symbol rate).
“N”
NASA36.
“X”
XR3 (25 Hz symbol rate).
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